Refrigeration system with liquid cooled condenser

ABSTRACT

A fluid cooled surface condenser of a compressor operated refrigeration system is continuously supplied with coolant at a constant predetermined flow rate irrespective of refrigerant flow variations in the closed refrigerant circuit of the system, and adequate head pressure on the high pressure side of the refrigerant circuit is maintained by controlled flooding of the condenser with refrigerant.

United States Patent Grant Apr. 30, 1974 REFRIGERATION SYSTEM WITH LIQUID COOLED CONDENSER [75] Inventor: Whitney I. Grant, Muskego, Wis.

[73] Assignee: Vilter Manufacturing Corporation, Milwaukee, Wis.

[22] Filed: July 26, 1972 [21] Appl. No.: 275,158

[52] US. Cl 62/181, 62/183, 62/196,

[51] Int. Cl. F25b 41/00 [58] Field of Search ,62/D1G. 17, 260, 196, 181, 62/183 [56] References Cited UNITED STATES PATENTS 2,267,607 12/1941 Harvey; ..62/D1G.17

3,389,576 6/1968 Mauer 62/D1G. 17 3,478,533 11/1969 Kocker... 62/D1G. 17 3,481,151 12/1969 Seeley 62/196 Primary Examiner-Meyer Perlin Attorney, Agent, or Firm-James E. Nilles [57] 7 ABSTRACT A fluid cooled surface condenser of a compressor operated refrigeration system is continuously supplied with coolant at aconstant predetermined flow rate irrespective of refrigerant flow variations in the closed refrigerant circuit of the system, and adequate head pressure on the high pressure side of the refrigerant circuit is maintained by controlled flooding of the condenser with refrigerant.

1 Claim, 4 Drawing Figures 437 46 FILTRATION 42 PLANT REFRIGERATION SYSTEM WITH LIQUID COOLED CONDENSER BACKGROUND OF THE INVENTION The invention relates to the condensing of heated and compressed gaseous substances and it is concerned more particularly with the condensing of the heated and compressed refrigerant vapor of a compressor operated refrigeration system.

In the refrigerating art, the use of fluid cooled surface condensers for refrigerant vapors is well known and has heretofore been common practice, particularly in commercial refrigerating plants. In installations using a shell and tube or other type of liquid cooled surface condenser, there is normally a source of liquid coolant that flows on one side of the condensing tubes, and the refrigerant vapors condense on the other side ofthe tubes. In order to control the head pressure of the refrigerant on the vapor side of such a fluid cooled condenser under varying refrigerating load and temperature conditions it has heretofore been common practice to install a regulating valve in the cooling fluid line together with a remote pressure sensing connection between the valve and the condenser. In operation, the valve throttles the flow of coolant through the condensing tubes so as to hold a substantially constant condensing pressure on the 'vapor side of the condenser. Where extremely low temperature condensing fluids are used, variations of the refrigerating load make it necessary to vary the flow rate of coolant through the condenser by means of the regulating valve within relatively wide limits. Also, where the coolant temperature varies considerably throughout the year, such as would be true with water as the condensing fluid where attimes the water temperature might be as low as 34 in the wintertime and as high as 85 in the summertime, the flow rate at which the condensing fluid is passed through the condenser must be varied within wide limits throughout the year, in order to insure proper operation of the system at all times. I

Experience has shown that fluid cooled surface condensers operate most efficiently when the condensing fluid flow rate is a constant and at the design conditions. At lower flow rates, there is a tendency particularly when a condensing fluid such as water is used, for the tubes to scale up and thereafter the condensing efficiency is reduced. For these reasons the use of pressure controlled regulating valves as heretofore common has not been very satisfactory. One disadvantage of their use has been a relatively low overall cooling efficiency of the condenser. Another disadvantage has been the need for relatively frequent cleaning of the condensing tubes and the resulting increase of maintenance costs.

SUMMARY OF THE INVENTION Generally, it is an object of the invention to overcome the hereinabove outlined disadvantages and shortcomings of the prior art with respect to the condensing of heated and compressed refrigerant vapors by means of a liquid cooled surface condenser.

More specifically it is an object of the invention to provide an improved compressor operated refrigeration system wherein cooling liquid is passed through a surface condenser at a constant flow rate which is so selectedthat not only the refrigerant cooling requirements of the system will be satisfied under maximum refrigerating load and coolant temperature conditions but also so that the coolant will constantly flow through the condensing tubes at a relatively high velocity which will suppress or at least significantly reduce objectionable scale build up or sediment accumulation within the tubes, and therefore eliminate the need for cleaning of the condensing tubes at objectionably frequent intervals.

A further objectof the invention is to provide an improved refrigeration system of the above mentioned character which will operate to automatically maintain a predetermined head pressure on the high pressure 'side of the refrigerant. circuit under widely varying retained at a constant rate undervarying refrigeration load and coolant temperature conditions, and wherein a predetermined pressure head is maintained on the high side of the refrigerant circuit by controlled flooding of the condenser with liquid refrigerant from the receiver.

These and other objects and advantages of the present invention will appear hereinafter as this disclosure progresses, reference b'eing had to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic view illustrating a typical refrigeration system having a liquid cooled surface condenser and embodying the present invention;

FIGS. 2-4 show three alternative cooling fluid supply systems which may be used in lieu of the cooling fluid supply system shown in FIG. 1.

i DETAILED DESCRIPTION The refrigeration system shown in FIG. v1 comprises, in general, a compressor 1, a liquid cooled surface condenser 2, a receiver 3, an evaporator 4, and a water pump 6. The compressor [is of-conventional multiple cylinder type and driven by an electric motor 7. Unloader solenoid valves 8 and 9 of the compressor are controlled by a multi-stage thermostat 11 which in turn is operatively connected witha temperature sensing bulb 12. A cooled space defined by an enclosure 13 houses the evaporator 4, the temperature sensing bulb l2,"an expansion valve 14 and a remote control bulb 16 at the outlet end of the evaporator, the bulb 16 being operatively connected with the expansion valve 14. A suction line 5 connects the'outlet end ofthe evaporator 4 with the suction side of the compressor 1 via a stop valve 10.

' The condenser 2 is a shell and tube type water cooled condenser. It consists of a cylindrical shell or drum l7, headers 18 and 19, and a number of straight tubes 21 between the headers through which a flow of cooling water is maintained. By means of partitions 22 in the headers water entering the condenser through an inlet port 23 in the heade r 18 is caused to flow back and forth through alternate groups of 'water tubes and to leave the condenser through an outlet port 24 in the header 18. A refrigerant inlet port 26 on top of the shell 17 is connected with the refrigerant discharge side of the compressor 1 by a hot gas discharge line 27 and stop valve 28; and a refrigerant outlet port 29 at the bottom of the shell 17 is connected with the receiver 3 by a drain tube 31.

The receiver 3 which in practice is mounted below the condenser 2, is connected with the expansion valve 14 by a system supply conduit 32 whose upper end terminates within the receiver 3 on a level below the lower end of the drain tube 31. The receiver 3 is convention-' ally equipped with a purge valve and a safety valve 20. An electric heater 33controlled by a thermostat 34 is mounted at the bottom of the receiver. Another thermostatically controlled heater 36 is mounted in the crankcase of the compressor 1.

In the embodiment of the invention shown in FIG. 1, cooling water for the condenser 1 is derived from a lake, river or other source of natural surface water generally designated by the reference numeral 37. The pump 6 is driven by a motor 39 and draws water from the water supply source 37 through a suction line 41. Operation of the pump 6 by the motor 39 forces a steady flow of water through a conduit 42, filtration plant 43, condenser feed line 44 including a hand operated globe or butterfly valve 46, condenser tubes 21, and condenser discharge line 47 including a hand operated globe or butterfly valve 48. The water discharged from the line 47 through the valve 48 may be returned to the source 37 through a sewer hub 49 and return line The design of the condenser 2and of its associated water supply system are determined by the cooling capacity of the refrigeration system as a whole. Given a desired maximum cooling capacity of the refrigeration system the design of the condenser and of the water circulating system are so coordinated that a steady flow of cooling water through the condenser will be continuously maintained at a rate which will satisfy the cooling requirements of the condenser under maximum refrigeration load conditions and at the highest temperature to which the cooling water is'expected to rise at any time throughout the year. As a further desirable requirement of the refrigerant cooling system according to the invention, the design of the condenser and of the water supply system are so coordinated that the velocity of the'water circulating through the condenser tubes at the required flow rate will be relatively high, as for example 200 feet per minute or such other value which will effectively suppress scale or sediment deposit in the condensing tubes.

For' proper functioning of a refrigeration system incorporating a constant flow coolant arrangement such as contemplated by the invention and as outlined hereinabove, provisions must'be made for maintaining a suitable pressure head on the vapor side of the condenser under varying refrigerating load and coolant temperature conditions. This result may be accomplished in various ways by controlled flood-ing of the condenser with refrigerant.

FIG. 1 shows a preferred arrangement to provide for constant rate by operation of the pump 6. The principal components of the controlled flooding arrangement shown in FIG. 1 are a condenser by-pass line 52, a differential pressure relief regulator 53 in the by-pass line, and an upstream pressure regulator 54 in the hot gas discharge line 27. I

In operation, as the temperature of the water circulating through the condenser tubes 21 falls, the condenser pressure will fall and the upstream pressure regulator 54 which is set at minimum system design pressure, for instance 210 psi, will modulate toward closed position to hold a constant upstream pressure at 210 psi. The differential pressure reliefregulator 53 is set to maintain a desired differential, for instance 25 psi. The regulator 53 will therefore hold the receiver at the difference between the pressure setting of the regulator 54 and the pressure setting of the regulator 53, which with the indicated values would be l psi. The drain tube 3l which dips into the liquid refrigerant within the receiver will permit someof the liquid refrigerant to be pushed up into the condenser because of the pressure difference. This liquid back-up will result in partial flooding of the condenser tubes with refrigerant and in a consequent reductionof the condensing surface. As a result of the diminished condensing surface the head pressure on the vapor side of the condenser will begin to rise. The regulators 53 and 54 will then modulate in the opposite direction until a state of equilibrium-is reached. Conversely, when the coolant temperature rises, the head pressure at the vapor'side of the condenser rises and the refrigerant level within the condenser will fall. The resulting increase of the condensing surface and operation of the regulators 53, 54 will adjust the cooling capacity of the condenser so as to maintain the required head pressure at the elevated coolant temperature.

Independently of or simultaneously with variations of the coolant temperature the refrigerating load conditions, that is, the requirements of heat removal from the cooled space of the enclosure 13 may vary. In that casethe head pressure in the condenser will be maintained at the desired value by raising and lowering the refrigerant level within the condenser in generally the same manner 'as has been described hereinbefore in connection with temperature variations of the cooling fluid. If the refrigeration load increases, the head pressure on the vapor side of the condenser increases and refrigerant is expelled from the condenser with a resulting enlargement of the condensing surface. Conversely, if the refrigerating load decreases, the head pressure decreases with a resultingdecrease of the condensing surface.

FIG. 2 shows a modified cooling fluid supply system for the condenser 2 shown in FIG. 1. In the system as shown in FIG. 2 cooling water is obtained from a well 52 and forced into thecondenser feed line' 44 by a submerged pump 53 and motor 54. The discharge side of the pump 53 is connected to the hand operated valve 46 of the condenser feed line 44 by a conduit line 54, and the condenser discharge line 47 is connected via hand operated valve 48 to sewer or other water uses.

FIG. 3 shows another modification of the cooling fluid supply system shown in FIG. 1. In FIG. 3 water or any other cooling fluid for the condenser 2 of FIG. 1 is derived from a cooling tower 56 having a sump 57, a spray deck assembly 58, and a motor driven fan 59.

Cooling fluid is drawn from the sump 57 of the cooling tower by a pump 61 which is driven by a motor 62.-The discharge side of the pump 61 is connected to the hand operated valve 46 of the condenser feed line 44 by a conduit 63, and the condenser discharge line 47 is connected with the spray deck assembly 58 of the cooling tower via hand operated shut-off valve 48 and conduit 64. Y

FIG. 4 shows still another modification of the cooling fluid supply system shown in FIG. 1 adapted for use of water or some other liquid as the cooling fluid. In FIG. 4 cooling fluid for the condenser 2 is derived from an auxiliary evaporative cooler generally designated by the reference numeral 66. The cooler 66 comprises a cooling coil 67 above a liquid pool 68; a spray deck assembly 69 above the coil 67 and a motor driven fan 71 above the spray deck 69. A pump 72 driven by a motor 73 has its suction side connected to the outlet end of the cooling coil 67, and the discharge side of the pump 72 is connected to the hand operated valve 46 of the condenser feed line 44 by a conduit 74. The condenser discharge line 47 is connected to the inlet end of the cooling coil 67 via hand operated valve 48 and conduit 76. While the pump 72 circulates cooling fluid at the predetermined rate through the refrigerant condensing tubes of the condenser 2 in FIG. 1, another pump 77 in FIG. 4 driven by a motor 78 circulates a separate cooling fluid through the evaporative cooler 66. While the pump 77 draws liquid from the pool 68 and delivers it to the spray deck 69, the fan 71 is kept running to draw air through the mist of cooling liquid which descends from the spray head assembly 69 into the pool 68. A float controlled valve 79 regulates the supply of make-up liquid to the pool 68. I

The coolant supply systems shown in FIGS. 2, 3 and 4, like the coolant supply system shown in FIG. 1 are each operable to continuously circulate coolant through the refrigerant condenser 2 at the flow rate at which the condenser 2 operates at its maximum efficiency. The coolant supply systems of FIGS. 3 and 4 lend themselves to operation with water or with any other suitable cooling liquid.

The principal control element which determines the flow of refrigerant through the refrigerant circuit of the system shown in FIG. 1 is the temperature sensing bulb 12. When. the temperature sensed by this bulb falls below the desired cooling temperature within the enclosure 13, the compressor 1 which is constantly driven by the motor 7 is loaded by operation of the thermostat 11 and of the solenoid operated unloading valves 8 and 9. Upon loading of the compressor the flow of refrigerant is controlled by operation of the expansion valve 14 and by controlled flooding of the condenser 2 with refrigerant from the receiver 3 in the manner described hereinbefore by means of the regulators 53 and 54. As

imum pressure is maintained in the receiver 3 and condenser 2, particularly when they are located outdoors, by means of the heater 33 and thermostat 34. The thermostat 34 is adjustable and set at such atemperature ential pressure regulator 53. In other words, the heater the refrigerant passes through the evaporator :4, the

33 should not be on when the compressorl is loaded and while the regulating valves 53, 54 are controlling. Setting of the thermostat 34 at too high a temperature would tend to-artificially raise the receiver pressure beyond what the regulators 53, 54 will allow for.

The herein disclosed invention is not limited to the use of water for condensing heated and compressed refrigerant in the condenser 2. If desired, other liquids may be used as the coolant, in which case heat removal therefrom may be effected by suitable equipment such as illustrated by FIGS. 3 and 4.

In summary, the herein disclosed refrigerating system is of the type wherein the necessary heat removal from the refrigerant under varying refrigeration load conditions is effected by the passage of a liquid cooling medium through a liquid cooled surface condenser.

More specifically, the system includes compressor control means as represented by the unloader solenoid valves 8 and 19, the thermostat 11 and the bulb 12,

rate and the cooling capacity of the condenser are rela- I tively so proportioned that the required heat removal from the refrigerant within the condenser under maximum refrigeration load and coolant temperature conditions will be effected by the passage of the coolant at said predetermined-flow rate through the condenser.

Finally, the system includes refrigerant flow control means as represented by the valves 14, 53 and 54 in the FIG. 1 embodiment of the invention; which are opera- I ble independently of the compressor control and pump means to regulate the flow of refrigerant through the evaporator and to automatically maintain a predetermined pressure head on the vapor side of the condenser under varying refrigeration load and coolant temperature conditions by controlled flooding of the condenser with liquid refrigerant from the receiver.

A significant feature of the invention resides in the factthat the flow rate at which the coolant is continuously passed through the condenser is kept constant and independent of the compressor control and refrigerant flow control means. Accordingly, the system does not require any flow control valves and associated actuating means for regulating the rate of coolant flow through the condenser under varying refrigeration load and coolant temperature conditions. The continuous passage of coolant through the condenser at the predetermined constant flow rate also has at least a retarding effect upon contamination of the condenser by scale build-up and fouling of the condenser tubes, thereby reducing the need for periodic cleaning of the condenser. I

I claim: 1 7

1. In a refrigeration system, the combination of arefrigerant compressor having a discharge conduit connected with the refrigerant inlet of a liquid cooled surface type condenser; compressor control means responsive to refrigeration load variations of the system to render said compressor alternately operative and inoperative; a receiver connected in liquid refrigerant receiving relation with said condenser and in liquid refrigerant delivering relation with an evaporator; a suction conduit connecting said evaporator with said compressor; a source of natural surface water and pump means operable independently of said compressor control means to continuously pass water from said source at a predetermined constant flow rate through said condenser; said flow rate and the cooling capacity of said condenser being relatively proportioned so that the required heat removal from the refrigerant under maximum refrigeration load and temperature conditions of said water will be effected by passage-of said water at said predetermined flow rate through said condenser; and refrigerant flow control means operable independently of said compressor control and water pump means to regulate the flow of refrigerant through said evaporator and to automatically maintain a predetermined pressure headon-the vapor side of said condenser under varying refrigeration load and temperature conditions of said water by controlled flooding of said condenser with liquid refrigerant from said receiver, said refrigerant flow control means comprising an upstream pressure regulator in said compressor discharge conduit; a condenser by-pass line extending be tween said receiver and a portion of said compressor discharge conduit intermediate said compressor and said upstream pressure regulator; a differential pressure relief regulator in said condenser by-pass line, and thermostatic means for heating said receiver to maintain a predetermined temperature therein. 

1. In a refrigeration system, the combination of a refrigerant compressor having a discharge conduit connected with the refrigerant inlet of a liquid cooled surface type condenser; compressor control means responsive to refrigeration load variations of the system to render said compressor alternately operative and inoperative; a receiver connected in liquid refrigerant receiving relation with said condenser and in liquid refrigerant delivering relation with an evaporator; a suction conduit connecting said evaporator with said compressor; a source of natural surface water and pump means operable independently of said compressor control means to continuously pass water from said source at a predetermined constant flow rate through said condenser; said flow rate and the cooling capacity of said condenser being relatively proportioned so that the required heat removal from the refrigerant under maximum refrigeration load and temperature conditions of said water will be effected by passage of said water at said predetermined flow rate through said condenser; and refrigerant flow control means operable independently of said compressor control and water pump means to regulate the flow of refrigerant through said evaporator and to automatically maintain a predetermined pressure head on the vapor side of said condenser under varying refrigeration load and temperature conditions of said water by controlled flooding of said condenser with liquid refrigerant from said receiver, said refrigerant flow control means comprising an upstream pressure regulator in said compressor discharge conduit; a condenser bypass line extending between said receiver and a portion of said compressor discharge conduit intermediate said compressor and said upstream pressure regulator; a differential pressure relief regulator in said condenser by-pass line, and thermostatic means for heating said receiver to maintain a predetermined temperature therein. 